-21.57% is the change from 51 to 40
Calculation steps:
[( 40 - 51 ) ÷ 51] x 100 = -21.57%
Formula
Percentage change = [(40 - 51) / 51] x 100
Subtract the new number by the original number
40 - 51 = -11
-11 ÷ 51 = -0.21568627450980393
-0.21568627450980393 x 100 = -21.57%